The two different configurations for Fourier transform systems are considered. Clearly, the converging beam Fourier transform (CB-FT) setup is simpler than conventional parallel beam setup (PB-FT), and it appears that it should be preferred in ordinary cases. But the advantage of the conventional configuration is to make the Fourier plane free of the spherical factor. In order to obtain an exact Fourier transform, the design of a holographic lens is described with respect to its aberrations.